ABSTRACT: The long-range objective of this project is to determine the role of interleukin 1 (IL1) and the related cytokines, interleukin 6 (IL6), tumor necrosis factor (TNF), and interferon-gamma (IFN-gamma) in the physiological and pathophysiological modulation of vascular tone. The proposed research will test the hypothesis that autocrine or paracrine actions of IL1 and/or IL6 produced within blood vessels modulate systemic vascular resistance and local blood flow in vivo. These studies will: (1) Determine whether IL6, TNF or IFN-1 act independently or synergistically with IL1 to induce nitric oxide (NO) production in cultured human vascular smooth muscle cells (VSMC). (2) Determine whether cytokines, including IL6, TNF, and/or IL1, are produced by VSMC and mediate the known activation of NO synthase in VSMC by bacterial endotoxin. This will be achieved by analysis of released cytokines using enzyme-linked immunosorbent assays (ELISA), and by immunoneutralization of cytokines using specific antibodies. (3) determine which vascular cell types and which vascular beds produce IL1 and IL6 in vivo, in both normal and LPS-treated rats, using in situ hybridization to detect IL1 and IL6 mRNA and immunocytochemistry to detect IL1 and IL6. (4) Determine whether second messengers or vasoactive agonists regulate IL1 or IL6 production and/or release by cultured human VSMC, using Northern analysis to measure IL1 and IL6 mRNA levels and ELISA techniques to measure IL1 and IL6. (5) whether IL1 induces endothelin gene expression in human VSMC in vitro. The proposal is based on my recent demonstration that IL1, a monocyte- and macrophage-derived cytokine, is a vasodilator which acts directly on vascular smooth muscle. In contrast to the rapid and transient actions of endothelium-dependent vasodilators, the effect of IL1 is slow in onset and prolonged, lasting hours to days. Preliminary studies further indicate that IL1 and IL6 are produced by vascular tissue in vivo. Therefore, autocrine actions of IL1 and IL6 produced within VSMC may play a significant role in long-term modulation of vascular tone. Furthermore, cytokines produced by either immune cells or vascular cells probably contribute to the vasodilatation associated with local inflammation, hemodialysis therapy, and septic shock, a major cause of human mortality. Understanding the roles of cytokines in modulating vascular tone may improve our ability to control these significant complications of human disease.